Be still means, don't worry. What this verse is saying is to not worry and understand God is in control. Even when the world is in what seems like a mess that can't be healed. God knows and understands just what is going on and has a plan. He offers us comfort and all we have to do is allow Him to give it to us. His arms are open wide. He wants everyone to have eternal comfort and peace. All you have to do is trust Him to give you that.
I know being still can be very hard to do. So many of us have some really hard things we are going through. Sometimes it's hard to see God in these situations. I promise he is there and wants to make everything beautiful from that hard time you are going through.
Have a blessed Sunday